Pulmonary complications due to smoke inhalation now are a major cause of death in burned patients. Curiously, the part played in the production of these complications by particulate matter (with or without adsorbed or adhered chemicals), as distinct from heat, irritating gases and steam, has not had adequate experimental evaluation. The proposed investigation will develop a reproducible experimental model for study of smoke inhalation, in which multiple variables can be controlled, and will define the role of particulate matter (and heat) in the pathogenesis of the changes known to occur in the early days following smoke inhalation, namely epithelial inflammation and ulceration, edema, congestion, and occlusion of the secondary and tertiary bronchi and alveoli, alveolar collapse distal to bronchiolar plugging and occasionally, massive atclectasis. It will also determine whether facial protection with materials commonly available at a fire scene (or readily and economically purchasable for mass use) can diminish those changes. Both protected and unprotected rats will be exposed in a controlled atmosphere to fixed doses of smoke at controlled temperatures and oxygen concentrations. Chamber air will be monitored by gas chromatography. Evaluation of results will be by mortality, changes in blood gases and autopsy findings, including histologic examination. During the later phases of this investigation, specific therapeutic measures to remove (or neutralize) the irritants will be developed and evaluated.